Development Of On-line Multiple Fault Injection Platform On Ship System

Ships usually run in particular and bad external environment, therefore,performances like safety, reliability and stability are quite important to the handlingcontrol system. Under the actual operating condition, kinds of faults could happenunexpectedly. For example, communication lines are easily interfered during theprocess of transmission, which cause several mistakes in communication. Also, erroraction of switch will influence the control system. Due to this special operatingenvironment, control system should be highly safe as well as reliable, thus system canmake correct decisions while fault happens. On-line fault injection platform on shipcontrol system is the large-scale significant device of security laboratory. On the basisof operating characteristics, a fault injection technique is proposed. By imitatingfaults which exist on real working condition, then artificially injecting these faultsinto the control system, fault-tolerance methods for ship handling control system withfaults can be researched and verified. Hardware and software platforms are providedfor researches about fault-tolerance method as well as testifying the effectiveness ofcontrol model. Research emphasis and achievements of the paper are as follows.(1) Research background and significance of on-line fault injection controlsystem are introduced. Research status of techniques including fault injection,fault-tolerance and digital filtering are illustrated in the paper. Requirements about theship handling control system are analyzed.(2) Theory and process of fault injection method are illustrated. Traditionalways of fault-injection trend to software injection, and the request of real time is noteasy to meet. Meanwhile, impedance faults resulted from displacement sensors can’tbe realized by software injection methods. To solve these problems, an on-linehardware fault-injection control platform is established. All kinds of faults areimitated through hardware circuits. It enables fault-injection technique stepping fromcomputer or control subjects to the area of electrical engineering. Overall designsolution of the control system is proposed. Fault injection devices and local controlunit are the two major parts of system. And redundant technique on sensors is alsoused to improve reliability of system.(3) According to the fact of interrupting running when it is needed to change thetype of injecting fault, an on-line technique is proposed. This method enables system to link and cut lines with power on, achieving real plug and play, and making systemmore flexible and reliable.(4) The integral hardware frame is established to imitate fault signals asswitching value, voltage analog signal, current analog signal and impedance analogsignal, which contain various usual faults or bugs during daily operating process.Since signals as flat noise, sine wave and so on are needed in fault injection circuits,the paper take flat noise signal for example. An approach of generating amplitudeadjustable Gauss flat noise signal is discussed. Different SNR flat noise signals can beacquired by changing variance yields. Then, hardware of ethernet communicationbetween computer and DSP is designed. It not only can realize control of DSP, butalso monitor operating condition of fault-injection circuits. By comparison of twodifferent circuit structures, the better construction of voltage analog signalfault-injection is chosen. At the same time, another three kinds of injecting circuitsare designed.(5) Software framework of system is established according to user’s requirements.It can be seperated into two parts, namely communication with computer and one withDSP. Developing and coding of software should be on the basis on three rules andeight steps. Software interface of the control platform is designed. Functionsincluding main program, channel searching, fault condition displaying, fault injecting,historical data query are realized. The interface is friendly and easy to operate. Then,communication process of DSP is shown in several flowcharts in detail.(6) Based on the ship valve control steering system, a recursive integral PIcompound control strategy is proposed. Mathematical modeling of valve controlsteering system is established. And closed loop transfer function is researched.Experiments and simulations prove the effectiveness of this strategy. In order tosmooth the sampling signals and improve reliability of the sampling system, a newmedian weighted average method is used, which performs very well on filteringinterference. In the end, hardware and software parts of the local control unit aredesigned separately.As mentioned above, the paper proposed an on-line multiple fault-injectioncontrol platforms of large ship control system, aiming at imitating all kinds of faultsunder marine environment. Fault injection and setting devices are responsible forinjecting those faults. Then, the local control unit collects data and sends them tofault-tolerant computer. Finally, closed loop controls of pump control and valvecontrol system are realized by the local control unit. Therefore, the control platform has great pratical significance in improving safety and reliability of ship system.